Combining Translation Readthrough Inducing Drugs and Nonsense Mediated Decay Pathway Inhibition to Rescue of CFTRW1282X in Cystic Fibrosis Cell Model System

Nonsense mutations affect about 11% of patients with Cystic Fibrosis and produce a premature termination codon in Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) mRNA causing early termination of the polypeptide translation. A potential therapy for nonsense mutations allows small molecules to overcome the premature termination codon (PTC) by a readthrough mechanism leading to the synthesis of a complete CFTR protein. However, the efficiency of the readthrough molecules is limited by a quality control cellular pathway known as Nonsense-mediated mRNA Decay (NMD). This pathway provides the degradation of the mRNA harboring a premature termination codon, to prevent the production of altered polypeptides. In contrast, the activity of this pathway interferes with the effectiveness of the readthrough drugs, limiting the CFTR mRNA amount to the rescue. In this work, we reduced the activity of the NMD pathway, silencing the Upf1 protein, one of the main components of the pathway. Our strategy was to increase the amount of the mRNA target to improve the efficiency of readthrough of TRIDs (Translational Readthrough Inducing Drugs) molecules in cells that ectopically express the W1282X-CFTR mRNA. The reduction of the Upf1 expression/activity was correlated with the increase of the efficiency of readthrough and so the increase of CFTR protein rescue.